What is Theocracy?

Legal Definition
Theocracy is a form of government in which a deity is the source from which all authority derives. The Oxford English Dictionary has this definition:

A form of government in which God (or a deity) is recognized as the king or immediate ruler, and his laws are taken as the statute-book of the kingdom, these laws being usually administered by a priestly order as his ministers and agents; hence (loosely) a system of government by a sacerdotal order, claiming a divine commission; also, a state so governed.

An ecclesiocracy is a situation where the religious leaders assume a leading role in the state, but do not claim that they are instruments of divine revelation. For example, the prince-bishops of the European Middle Ages, where the bishop was also the temporal ruler. Such a state may use the administrative hierarchy of the religion for its own administration, or it may have two 'arms' — administrators and clergy — but with the state administrative hierarchy subordinate to the religious hierarchy.

The papacy in the Papal States occupied a middle ground between theocracy and ecclesiocracy, since the pope did not claim he was a prophet who received revelation from God and translated it into civil law.

Religiously endorsed monarchies fall between theocracy and ecclesiocracy, according to the relative strengths of the religious and political organs.

Most forms of theocracy are oligarchic in nature, involving rule of the many by the few, some of whom so anointed under claim of divine commission.
-- Wikipedia
Legal Definition
A species of government which claims to be immediately directed by God.

2. La religion qui, dans l'antiquite, s'associa souvent au despotisms, pour regner. par son bras ou a son ombrage, a quelquefois tents de regner seule. Clest ce qu'elle appelait le regne de Dieu, la thiocratie. Matter, De l'influence des Moeurs sur les lois, et de l'influence dos Lois sur les moeurs, 189. Religion, which in former tinies, frequently associated itself with despotism, to reign, by its power, or under its shadow, has sometimes attempted to reign alone, and this she has called the reign of God, theocracy.
-- Bouviers Law Dictionary
Legal Definition
Government of a state by the immediate direction of God, (or by the assumed direction of a supposititious divinity,) or the state thus governed.
-- Black's Law Dictionary
Legal Definition
A government recognizing God as its ruler.
-- Ballentine's Law Dictionary